The grant, Endocrine Factors in the Development of Plasmacytoma is searching for the locus of the hormonal action on the different phase of the pathogenesis of plasmacytomas in mice. The grant tries to relate the hormonal action to 2 other factors suggested by us as being involved in the pathogenesis of PCT: lipopolysaccharide (LPS) and a pristane-induced peritoneal exudate (PIPE). In vivo and in vitro experiments leading to understanding of the hormonal modulation of LPS and PIPE mechanisms of action are presented.